When the Tropical Rainfall Measuring Mission (TRMM) satellite flew over Tropical Storm Sonca on Friday, Sept. 16 it found moderate rainfall mostly on the southern side of the storm. Chichi Jima can expect some of that rainfall over the weekend as Sonca passes east of the island.

TRMM passed over Tropical Storm Sonca and its precipitation radar instrument saw moderate rainfall occurring mostly on the southern side of the storm, while light-to-moderate rainfall was occurring throughout the storm. The southern edge of the storm had rainfall rates between .78 to 1.57 inches (20 to 40 mm) per hour. The TRMM satellite is managed jointly by NASA and the Japanese Space Agency.

At 11 a.m. EDT on Sept. 16, Tropical Storm Sonca had maximum sustained winds near 45 knots (52 mph). It was centered about 500 nautical miles east of Iwo To, Japan, near 23.5 North and 149.4 East. Sonca was moving to the west at 15 knots.

NASA's Aqua satellite has been flying over Sonca, and the Atmospheric Infrared Sounder (AIRS) instrument has been providing infrared imagery and temperature data of the storm. Infrared imagery has shown convection (rapidly rising air that forms the thunderstorms that power the tropical cyclone) around Sonca's center, in addition to bands of thunderstorms wrapping into the center. There is, however a good amount of dry air streaming into the western quadrant of the storm, which suppresses thunderstorm development. Infrared data has also shown that the sea surface temperatures are around 27 Celsius (just over 80 Fahrenheit) and warm enough to maintain a tropical cyclone.

The Joint Typhoon Warning Center has forecast Tropical Storm Sonca to make an easterly pass by the island of Chichi Jima over the weekend and then head to the northeast into the open waters of the western North Pacific Ocean.